Question

12(d). A sample of radioactive substance was found to be left with 1/32 of its initial count rate after 110 years. Calculate its decay constant.

Accepted Answer

Using N = N₀e⁻λt with N/N₀ = 1/32 and t = 110 years:
1/32 = e⁻λ(110). Taking natural logs: ln(1/32) = −λ(110) → −λ(110) = −3.4657 → λ ≈ 0.0315 per year (approximately 0.03 yr⁻¹).

WAEC Physics 2015 Theory — Question 26

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